Abstract: Through analysis of the field scale samples in Wuqi oilfield by X-ray diffraction method,scaling causes and scale control measures are studied in downhole and gath- ering system.The experimental results indicate that scal- ing components are mainly carbonate scale.The causes are the decrease of CO2 partial pressure during oil produc- tion,the mixture of two types of incompatible produced water in commingled production well,the increase of tem- perature by heating for demulsification or transportation of produced fluid.The optimized SIB scale Inhibitor can effectively inhibit scale buildup of produced water and greatly lengthen the period of scale removing in gathering system by field application.